The present invention relates to a vapor deposition film with excellent adhesion of a vapor deposition layer and to a packaging material using the same, and more specifically relates to packaging materials used for packaging in the fields of foods, non-foods, medicines and so forth, as well as a vapor deposition film used for such packaging materials, and particularly to packaging materials used in packaging fields which require boiling sterilization, retort sterilization, autoclave sterilization and the like, and to a vapor deposition film used for such packaging materials.
In recent years packaging materials used for packaging of foods, non-foods, medicines, etc. must have the ability to block the effects of oxygen, water vapor and other gases which permeate the packaging materials and alter the quality of their contents, in order to prevent such alteration in the contents and maintain their functions and properties. Hence there is a demand for packaging materials with gas barrier properties which block these gases. Commonly used packaging materials to date have therefore employed metal foils of aluminum, etc. as gas barrier layers, because they are largely unaffected by temperature and humidity.
Nevertheless, while packaging materials employing aluminum and other metal foils have excellent gas barrier properties, problems have existed because of their drawbacks, which include the fact that such packaging materials are not transparent enough to allow visual verification of their contents, that they must be treated as non-combustibles when disposed of after use, and that metal detectors cannot be used for their examination.
As packaging materials designed to overcome these drawbacks there have been developed films wherein silicon oxide, aluminum oxide, magnesium oxide or another inorganic oxide vapor deposition film has formed on a polymer film by a forming means such as vacuum vapor deposition or sputtering, as is described, for example, in U.S. Pat. No. 3,442,686, Japanese Examined Patent Publication No. Sho 63-28017, etc. Such vapor deposition films are known to be transparent with gas barrier properties against oxygen, water vapor and the like, and are thus suitable as packaging materials which provide both the transparency and gas barrier properties which are unobtainable with metal foils, etc.
However, although such films are suitable for the packaging materials described above, virtually none of them can be used as vapor deposition films alone for packaging containers and packaging materials. This is because packages are completed by undergoing post-processing after vapor deposition, which involves various steps such as printing of characters and images on the vapor deposition film surface, or attachment to other films, etc. and shaping into packages for containers and the like. In particular, because packaging materials subjected to boiling sterilization, retort sterilization or autoclave sterilization are sterilized through many different steps, due care must be taken in designing such packaging materials.
When attempts have been made to use these types of vapor deposition films in combination with sealant films to prepare bags which are then filled with contents and subjected to boiling sterilization or retort sterilization, peeling of the vapor deposition layer has occurred at parts of the sealed sections resulting in a poor outer appearance, while the gas barrier properties are also reduced at those sections, leading to alteration in the quality of the contents.
In other words, the conditions for packaging materials in such situations include transparency which allows the contents to be directly viewed, high gas barrier properties to block gases which adversely affect the contents, and resistance to sterilization treatment with no deterioration of the gas barrier properties and no peeling after boiling sterilization, retort sterilization and autoclave sterilization; at present, however, no packaging materials have been discovered which satisfy all of these conditions. The conventional packaging materials have also had the problem of deteriorating water resistance, and especially poorer laminate strength after exposure to water.
It is a first object of the present invention to provide a vapor deposition film which allows direct viewing of contents and which has high gas barrier properties comparable to those of aluminum foil. In particular, there is provided a vapor deposition film which exhibits no peeling of the vapor deposition layer from the substrate or deterioration of its gas barrier properties even after boiling sterilization or retort sterilization, and without loss of laminate strength after exposure to water, thus promising a wide range of possible uses in packaging materials with general usefulness for foods, non-foods, medicines and the like.
It is a second object of the invention to provide a packaging material made using this vapor deposition film, which is a highly practical packaging material with high gas barrier properties and with high resistance to sterilization, undergoing no loss of its properties and no peeling of the vapor deposition layer from the substrate even after boiling sterilization or retort sterilization.
It is a third object of the invention to provide bag-like packages made using the packaging material, which are packages which undergo no deterioration in oxygen permeability or laminate strength after sterilization treatment, and which exhibit virtually no peeling of their vapor deposition layers from their substrates.
In order to achieve the objects described above, the present invention provides a vapor deposition film comprising a substrate made of a transparent plastic material, a primer layer comprising a composition which contains a trifunctional organosilane represented by the general formula Rxe2x80x2Si(OR)3 (wherein Rxe2x80x2 is a substituted or unsubstituted alkyl group, vinyl group, etc. and R is an alkyl group, etc.) or a hydrolysate of the organosilane, an acryl polyol and an isocyanate compound, and a vapor deposition layer comprising an inorganic oxide in a thickness of 5xcx9c300 nm, formed by successive lamination on at least one side of the substrate.
The present invention further provides the aforementioned vapor deposition film wherein Rxe2x80x2 in the trifunctional organosilane is an alkyl group including an epoxy group or isocyanate group.
A reaction catalyst is preferably added to the aforementioned composition for the primer layer. In particular, the reaction catalyst may be a tin compound, and is preferably a tin compound selected from the group consisting of tin chloride, tin oxychloride and tin alkoxides.
It is preferred to further add to the composition a metal alkoxide represented by the general formula M(OR)n (wherein M is a metal element, R is an alkyl group such as CH3, C2H5, etc. and n is the oxidation number of the metal element) or a hydrolysate of the metal alkoxide. Here, the metal of the metal alkoxide is preferably a metal selected from the group consisting of Si, Al, Ti, Zr and their mixtures.
The thickness of the primer layer is preferred to be in the range of 0.01xcx9c2 xcexcm.
The inorganic oxide of the vapor deposition layer is preferably one selected from the group consisting of aluminum oxide, silicon oxide, magnesium oxide and their mixtures.
An overcoating layer may be also laminated on the vapor deposition layer, and it is preferred for the overcoating layer to be a layer obtained by applying, heating and drying a coating agent composed mainly of an aqueous solution or an aqueous/alcohol mixed solution containing a water-soluble polymer and either or both (a) at least one metal alkoxide or hydrolysate thereof and (b) tin chloride. Here, the metal alkoxide is preferably one selected from the group consisting of tetraethoxysilane, triisopropoxyaluminum and mixtures thereof. The water-soluble polymer is preferably polyvinyl alcohol.
The invention still further provides a packaging material prepared by laminating the aforementioned vapor deposition film and a heat seal layer on the vapor deposition layer or the overcoating layer side.
The invention still further provides packages made into bag form using the aforementioned packaging material.